The subject matter described herein relates generally to methods and systems for a wind turbine including a cable, and more particularly, to methods and systems for sensing conditions in a cable of a wind turbine.
Generally, a wind turbine includes a turbine that has a rotor that includes a rotatable hub assembly having multiple blades. The blades transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are sometimes, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Gearless direct drive wind turbines also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on top of a base that may be a truss or tubular tower.
Some wind turbine configurations include double-fed induction generators (DFIGs). Such configurations may also include power converters that are used to convert a frequency of generated electric power to a frequency substantially similar to a utility grid frequency. Moreover, such converters, in conjunction with the DFIG, also transmit electric power between the utility grid and the generator as well as transmit generator excitation power to a wound generator rotor from one of the connections to the electric utility grid connection. Alternatively, some wind turbine configurations include, but are not limited to, alternative types of induction generators, permanent magnet (PM) synchronous generators and electrically-excited synchronous generators and switched reluctance generators. These alternative configurations may also include power converters that are used to convert the frequencies as described above and transmit electrical power between the utility grid and the generator.
Known wind turbines have a plurality of mechanical and electrical components. Each electrical and/or mechanical component may have independent or different operating limitations, such as current, voltage, power, and/or temperature limits, when compared with other components. Moreover, known wind turbines typically are designed and/or assembled with predefined rated power limits. To operate within such rated power limits, the electrical and/or mechanical components may be operated with large margins for the operating limitations. Such operation may result in inefficient wind turbine operation, and a power generation capability of the wind turbine may be underutilized.
The electrical energy generated by the generator is transported to the users of electrical energy. For this purpose, wind energy systems have export cables connecting a wind farm to a power grid. In the case that the wind energy system is located in the sea, that is, the wind energy system is an offshore wind energy system, the cable connected to the power grid is at least partly a submarine cable. Although the cables are protected by being buried under the sea bed, extreme waves, currents, and sea bed movements can expose the cables and leave them vulnerable to the hydrodynamic forces of the sea. Furthermore, accidents with ships, for instance, by anchors of fisher boats, or earthquakes can damage the cable of an offshore wind turbine beyond repair.
Approximately 10% of the investments for an offshore wind farm are used for submarine cables. Broken cables have a great effect on the availability of the wind farm. Furthermore, the time span for repair activities concerning the submarine cables is in the range of several weeks, inter alia due to difficulties in finding access to the cable.
Thus, there is a desire for a cable for an offshore wind turbine which facilitates maintenance and repair and also saves time as well as costs caused by the maintenance and the repair.